This invention relates to a fillet rolling tool for deep rolling journal fillets, and more particularly, the invention relates to an improved work roller cage for the fillet rolling tool.
Deep rolling has been used for many years to strengthen the journal fillets of components such as engine crankshafts. The fillets are mechanically worked and plastically deformed by a rolling tool to strengthen the fillets and relieve stress in the area of the fillets. Typically, a pair of opposing work tools are used to roll the journal fillets. One tool includes a pair of rollers to support the lower portion of the journal while an upper tool containing at least one work roller is used to engage the journal fillet and mechanically work the fillet area. The upper and lower work tools are actuated towards one another using a hydraulic cylinder to apply pressure in the area of the journal fillet. The work piece, such as a crankshaft, is driven along its axis to roll the journal fillets. The work roller is subjected to several thousand pounds of force during the deep rolling process.
The work rollers are supported on the upper work tool by cages that retain the work rollers. The cages have arcuate recesses that are defined by inner and outer walls and receive the work roller. The work rollers are permitted to float laterally to compensate for tolerances in the crankshaft. For at least the last several decades the cages have been constructed from bronze. During the deep fillet rolling process due to the lateral motion of the work roller within arcuate recess of the cage, the outer wall of the cage may fracture thus necessitating replacement of the cage. As a result, production of crankshafts must be interrupted so that the upper work tool may be removed and the cage replaced. Therefore, it is desirable to provide an improved cage that does not fracture during lateral movement of the work rollers within the cage.
The present invention provides a fillet rolling tool for deep rolling journal fillets. The tool includes a housing assembly having a cavity. A backup roller having an annular groove is disposed in the cavity and is rotatably supported by the housing assembly. A work roller is received in the annular cavity for deep rolling journal fillets. At least one cage, constructed from a polymer material, has an arcuate recess that receives the work roller. The cage includes an outer wall that defines a portion of the arcuate recess. Preferably, the polymer is a thermoplastic such as a high density polyethylene. Most preferably, the polymer is an ultra high molecular weight polyethylene. The polymer of the present invention has a ductility, an impact strength, and a wear resistance that is superior to those of bronze. Accordingly, the polymer cage of the present invention does not fracture as easily as bronze under the lateral forces of the fillet rolling process.